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Case
of the Week #44

Clinical
history

A twenty year old woman complained of right sided abdominal
pain and right shoulder pain for five days after delivery of her first child. A CT scan showed a lesion near the dome of the liver. Several biopsies were obtained:

A
trichrome stain confirmed the presence of fibrosis within the portal tracts.
An iron stain showed no evidence of increased iron stores.

What
is your diagnosis?

(scroll
down to continue)

Diagnosis:

Inflammatory
pseudotumor of the liver

Discussion

Inflammatory
pseudotumor is also called inflammatory myofibroblastic tumor. The diagnosis includes
both reactive and neoplastic conditions. Although common in the lung, it is
rare in the liver. The mean patient age is 37 years, but all ages are affected.
75% of patients are male.

Grossly,
the tumors are usually well circumscribed, and 70% are solitary. Tumors may
extend into the inferior vena cava or retroperitoneal soft tissue. They have a
variegated cut surface, often with hemorrhage and necrosis.

Microscopically,
the tumors consist of a mixture of inflammatory cells, particularly polyclonal
plasma cells, lymphocytes, eosinophils and macrophages. Neutrophils may also
be present. There are also variable amounts of plump spindled cells resembling
myofibroblasts and mature fibroblasts. The stroma is often whorled, resembling
leiomyoma or fibrotic resembling sclerosing hemangioma. Mitotic activity is
rare.

The
spindled cells are immunoreactive for vimentin, smooth muscle actin and muscle
specific actin in 80% of cases. There is variable immunoreactivity for desmin
and pankeratin stains. These tumors are negative for S100, CD21 and CD35. A
small percentage are ALK+, which is associated with a favorable prognosis at
all sites combined (Am
J Surg Pathol 2001;25:761).

The
differential diagnosis is large. First, if the excision is subtotal, the diagnosis
must be considered tentative, as other neoplasms may have a similar inflammatory
component. Second, dendritic cell tumors must be excluded. They usually occur
in women, often have systemic symptoms and are immunoreactive for follicular
dendritic cell markers CD21 and CD35. The inflammatory tumor-like variant is
usually associated with Epstein-Barr virus infection (Am
J Surg Pathol 2001;25:721). Third,
infectious disorders, such as TB, syphilis or bacterial abscess may cause an inflammatory
infiltrate, and antibiotics or NSAIDS may cause tumor regression (Acta
Gastroenterol Belg 2005;68:382, Scand
J Gastroenterol 2005;40:875, J
Clin Pathol 2003;56:868).
Fourth, inflammatory disorders such as sarcoidosis, malakoplakia, abscess and
cholangiohepatitis should be considered. Finally, tumors to consider include
sclerosing hemangioma, leiomyoma, solitary fibrous tumor, sarcomatoid
carcinoma, nerve sheath tumors, Hodgkin’s lymphoma and MFH. Post-operative
spindle cell nodule is similar morphologically, but has a different clinical
history.

A
recent study suggests that cases associated with sclerosing cholangitis may
represent an IgG4 related biliary disease that is part of the spectrum of
sclerosing pancreatitis and is responsive to steroids (Am
J Surg Pathol 2004;28:1193).